Massive defensive buildings, residential areas along an inner ditch, industrial kilns and furnaces and evidence of quarrying have been found at Old Sarum, a mysterious medieval city in Salisbury built during the Iron Age and used as a fortification for 300 years before disappearing during the 13th century.

No plan has ever been made of the city, which has origins around the time of the Roman conquest. But archaeologists have used modern technology to subtly plot its layout and buildings, revealing that a circular route would have provided access around a “thriving” site.

“Our research so far has shown how the entire outer bailey of the monument was heavily built up in the Middle Ages, representing a substantial urban centre,” says Kristian Strutt, who is part of a team from the University of Southampton with designs on continuing their investigations next year following a productive summer of discoveries.

“Results have given us compelling evidence as to the nature of some of the structures. It is clear, however, that there is more non-intrusive work that could be carried out to further expand our understanding of the site.”

Heather Sebire, a Property Curator at English Heritage, which owns Old Sarum and invited the archaeologists to explore, describes the initial findings as a “great start” to an intriguing story.

“Having the team of archaeologists on site over the summer gave our visitors a chance to find out more about how important historic landscapes are surveyed,” she says.

“From this work we can surmise much about the site’s past.

“While we can’t conclusively date the findings, it adds a new layer to Old Sarum’s story.”

Magnets, earth resistance, electric tomography and radar systems were used during the survey, which repeated techniques used effectively at landmarks including Bishop’s Waltham Abbey and Bodiam Castle.